1. Technical Field
The present invention relates to an X-ray generator suitable for a fluorescent X-ray analyzer that can detect harmful substances and is used for screening a product or measuring thickness of a film such as a plated layer, and a fluorescent X-ray analyzer having the same.
2. Description of the Related Art
Fluorescent X-ray analysis is a process wherein X-rays are radiated to a specimen from an X-ray tube, fluorescent X-rays coming out of the specimen are detected using an X-ray detector, and components of the specimen is qualitatively analyzed or concentration or film thickness is quantitatively analyzed from the intensity relationship of the X-rays. Fluorescent X-ray analysis makes it possible to quickly and nondestructively analyze a specimen, so it is used in various fields including process/quality management. In recent years, with the development of precision and sensitivity, fluorescent X-ray analysis can measure small amount of a substance and is expected as an analysis technique to detect harmful substances, particularly in materials or composite electronic parts.
In general, a fluorescent X-ray analyzer that analyzes a range of tens to hundreds of micrometers by narrowing primary X-rays to be radiated to a specimen into a narrow beam is equipped with a device for limiting an X-ray radiation area and an X-ray tube that is an X-ray source (hereafter, referred to an X-ray radiation area controller or a condensing element). For example, there is a fluorescent X-ray analyzer equipped with a poly-capillary that can reduce a radiation area on a specimen by condensing X-rays from an X-ray tube. The poly-capillary is a device that is composed of a bundle of hollow glass tubes (capillaries) having an inner diameter of about 10 μmm and condenses X-rays by totally reflecting incident X-rays from the inner side such that the exits of the capillaries focus on one point.
It is required to make sure that the X-ray generation position in the X-ray tube and the X-ray radiation area controller are precisely aligned. However, the temperature around an X-ray tube changes in a predetermined range in many cases due to various factors such as the installation environment of the apparatus, heat generation in the case of the tube, and a temperature change in the case due to opening/closing of a door. Due to this change, the amount of thermal deformation of the anode of the X-ray tube is usually changed, and accordingly, the X-ray generation position is changed.
That is, the temperature of an X-ray tube is not uniform throughout it due to the output, the environment temperature, and the temperature in the case of the apparatus and the X-ray tube thermally deforms due to the temperature change, so the mechanical position of the X-ray generator changes. Accordingly, in an apparatus for radiating X-rays to a specific small area and analyzing fluorescent X-rays coming from the area, a mechanical change of an X-ray generation position causes misalignment of a device for radiating X-rays to the specific small area, so the X-ray radiation position or the intensity of the X-rays is changed.
For example, when a poly-capillary is attached and fixed to an X-ray source, condensing efficiency (intensity of output from the poly-capillary) depends on the attachment position of the poly-capillary, and maximum output intensity is achieved when the poly-capillary is disposed directly under the X-ray generation position relative to the target of the X-ray tube. In this case, when the relative position between the X-ray source and the poly-capillary changes due to a mechanical factor or heat (temperature drift), the output intensity is reduced. In particular, the output intensity is sensitive in the horizontal direction perpendicular to the central axis of the poly-capillary. For example, the output intensity is reduced by 5% point when it moves 10 μm in the horizontal direction.
These changes have conventionally been handled by suppressing a change in atmospheric temperature through interior air-conditioning or by performing corrective measurement for frequently correcting an effect of temperature change, but they are insufficient.
In relation to these problems, a system for moving a target of an X-ray tube by heating/cooling the target in accordance with a change in surrounding temperature and for correcting position alignment due to a temperature change have been proposed in Patent Document 1.